An IP address is a unique number that identifies an Internet site or a hosting server on the Internet, so if you have a dedicated IP, it will be employed solely by your websites and won't be shared with other people as it happens with shared hosting accounts. Provided you have your own server, you'll have a dedicated IP, but you may require extra ones for a variety of uses. In case you have an online store, for instance, you shall need an SSL certificate for it, so as to ensure that the payment information which your customers submit will be encrypted and protected. The same is valid in case you have a login form of some sort and you want the usernames and the passwords that visitors input to be secured. The SSL certificate requires a dedicated IP, which ought to be different from the one which you already have on the hosting server. You might also need an independent IP for an app such as a VoIP server, or if you need a slightly better efficiency for a given Internet site, which may influence its position in search engine results.